The Impossible, True
by Michi.C27
Summary: In a world where the touch of an angel and a demon causes blistering pain to both, Dean and Castiel have fallen in love with each other and they must fight through the pain to be together. Demon Dean, Angel Castiel, Destiel, shameless smut, painful sex, blow job, mild face-fucking, anal sex, rough sex, sex with feelings, bottom Dean, top Castiel, bottom Castiel, top Dean, Switching


**Author's Note**

 _Forewarning: this is not meant to be any kind of pain kink fic. It hurts to be together and not in a good way, but they deal with because they can't live without each other._

 _Also, most of this will be superfluous information since there isn't much plot at all (seriously, it's basically porn), but I feel I should tell you that this is not canon. It's a world where there are no vessels; demons are born and angels were created with the bodies we see them with. So Dean and Sam have been demons all their lives, embut/em John rebelled from hell after Mary died, and Sam and Dean still grew up as hunters, just Demon!Hunters._

 _They're also older than canon, but still not as old as Cas. Once demons (or angels) reach their physical peak and maturity, they stop aging. So go ahead and picture season 9/10 Cas and Dean ;]_

 _This can absolutely be read as a stand-alone, but I have written a part two as well (should be posted by 3/8/18)_

 _Enjoy! Please let me know what you think in the comments. Comments are love :3_

* * *

"Mnngh, come on!"

It burned, _god_ , it burned, thick slide pounding harder, deeper in his heat, his burning, scorching heat, and the trembling sweft of fingers and skin and skin and skin pressed down on him, everywhere and inside of him. "Oh God in heav-" Wet muscle pushed into his mouth sparking cracks of jolting pleasure down his jaw in a shocking dichotomy of cool relief and hot pleasure, the _Ungh_ an aborted growl above him half of pain and half of ecstasy.

Dean understood and cried at it because it _hurt_. It hurt, it hurt, it hurt, and still, he pulled his angel closer, slicked inside his mouth, twisted their tongues together, closer, closer, closer, shaking as their bodies writhed.

"Need you," he hissed.

"Saints," Castiel growled, the closest he would come to blasphemy. It meant he was close, so close. " _Dean_."

A blind shatter of pleasure up Dean's spine threw his head back and bent his body, keening high. "Ca-gaaahd-" he clamped his teeth because Cas didn't stop punching him, _right there_ , grinding, thrust, thrust, thrust -He wanted to scream, he wanted to cry-it hurt-it-oh, god, it felt so good-overwhelming, shooting-

He screamed as he came, feeling the grunt, grunt, grunt of Cas pounding his ass, and then the whimper, high and desparate as hot cum gushed inside. His cock spasmed at the feeling, shooting another stripe of white across their chests as he lay, dizzy in pleasure.

* * *

It was stolen. This moment. It was always stolen. Between the hunts. Between the days. Between the hours. Anywhere, everywhere, whenever they could, however, it didn't fucking matter. As long as they could touch. As long as they could stand the burn.

* * *

Drumsticks beat the clouds, rain pummeling the roof like the uncoordinated march of a demon army. The drip, drip, drip from the narrow awning splashed in Dean's hair, trickled down his neck, made a line between his shoulderblades, and soaked the waistband of his jeans.

Nobody liked being wet-Dean did not like being wet-but, hell, inside wasn't much better in this shack anyway. And besides, Cas would be there soon. He'd fly from heaven with his perfect shadow wings and his perfect holy body and Dean was so ready to see him. It had been way too fucking long and he needed-

No. No, no. Dean didn't _need_ anybody. Despite what he had said last time Cas had fucked him into oblivion. _That_ was his dick talking, and he couldn't be blamed for that. Even if he did love him. With every fucking particle of his being-God, he was screwed. He dragged his hand through his damp hair and leaned on the wooden porch post, trying not to throw up. He just - he needed to _see_ him, okay? His skin already itched with the burn of Castiel's touch, he _smelled_ the soft musky scent of his skin, even as he stood outside in the rain and his nose ran. He needed to see him. He was ready, so beyond ready when he heard him, the telltale beat of shadow wings. Dean's stomach flipped.

It took his eyes a second to find him through the darkness and the rain, and then there he was. Out in the rain, looking rumpled and grumpy until he saw Dean. Even from here he could see how his eyes lit up.

 _Perfect. He's so perfect and I don't deserve him._

Despite that thought, he plunged into the rain, running faster than Cas was towards him. They collided somewhere in the middle and that first, that very first touch was always the worst as heaven met hell. It was like a spark and burn that rippled up his arms and cramped his muscles and choked a cry from both of their throats. For less than a second, they recoiled on instinct, fighting against the wave of agony... And then they were back and the burn followed wherever they touched, painful and _wrong_ , like two magnets repelling by biology and slamming back together through will. And it hurt. It hurt, it hurt, but it was _worth_ it. Worth the pain of the arms wrapped around him, trapping him close, and worth the pain as Dean's elbows locked around his neck and Cas let out little hurt whimpers, and worth the pain as he clawed his fingers into that hair, and even when he dragged their mouths together and their lips crushed and chapped and burned and they both let out groans that were more pain than pleasure on first contact, it was _worth_ it. They both lapped and crooned before Dean licked past those lips and their tongues coiled together and the pain was shoved down and pushed past in favor of _this_. This desperate connection because neither of them were fucking _close enough_ and _it had been too fucking long._

" _Cas_ ," Dean whimpered between broken kisses. The arms around his waist tightened, fingers clawing in cotton in lieu of any kind of response besides a deep groan of need until their lips were connected again, plush and straining against the contact, angel grace and demon blood fighting to heal their bodies of every press.

"Missed you," Cas breathed and bit, working Dean's rain and kiss-spit lip between his teeth, before soothing it with his lips and taking Dean's mouth with his tongue. They kissed and kissed for several seconds, unwilling, or maybe even unable, to pull away, to form words until Dean was scratching Castiel's scalp and their hips were thrusting out of sync, pounding the air and occasionally each other. Castiel groaned and pecked his lips. "Need you."

"Me too," Dean whispered because he was fucking liar, and yeah, he needed Cas, okay? The salty burn on his face, hidden by the rain and the taste in his mouth and the way he couldn't fucking think beyond _Cas, Cas, Cas_ , made that fairly flippin' obvious.

"In there?" Cas asked, looking over his shoulder at the shack before kissing up Dean's jaw, leaving a trail of heat in his wake.

"Well we're not doing it in the rain." Castiel blinked and looked up as if he hadn't even noticed, and Dean spared a second to roll his eyes at his angel before he let his hand drop down to Cas' and pulled him after him, running through the rain, stumbling into the leaky shack and shoving Cas against the door. He chuckled because Cas looked like a soggy, happy puppy, and then he was kissing him again. And the water sizzled wherever they touched, boiling bruises and burns that would heal if they gave each other a second apart. But neither was willing. Even for that second, and the burns and the bruises and the blisters came and went to the accompaniment of their groans as they reveled in each other, fighting past the pain because it was _worth it_ to be together.

The shack was old and deserted and dripping from holes in the roof, but the bed in the corner was covered in new sheets-heck, it was a new mattress Dean had mojoed from some store a thousand miles from here. Somebody would come into work tomorrow and find everything as it was, except for a single bed set missing. And if that wasn't funny Dean didn't know what was.

"Come on," Dean breathed, shedding Castiel of his sodden coat and pulling him in the right direction, before they came together again, distracted, kissing, clawing at clothes, and then stumbling back. Cas slammed Dean against the wall once, breaking wood as Cas, two layers gone, now in suit shirt and tie, pushed him into the wall and rubbed his knee over Dean's straining cock.

Their shoes crunched on leaves and other small dead things before they tumbled, shirtless onto the mattress, Castiel above him, framing him, kissing blisters on his chest and neck.

"You're soaking wet," he mumbled, as he licked a stripe up his throat and framed his head with his arms, looking down at him with this focused expression, even as their bodies rocked together hard, seeking friction, seeking each other. Pleasure gripped Dean's spine at the feel of Cas pressing down on him but he chuckled anyway.

"I dunno if you've noticed, handsome, but likewise." A drop of water fell from the black tufts of Castiel's hair even as he spoke and singed a marked on Dean's cheek. " _God_ ," he hissed as their cocks rubbed through too much material. It would honestly take a split second for either of them concentrate long enough to make them dry. But after a month and none of each other, they didn't fucking have time for that.

He grabbed Cas, hooked a knee around his waist, and in one smooth move, flipped them over. "I need to touch you," he growled and then whined as his trembling fingers yanked at the suit pants around Castiel's hips. "I need to taste you."

" _Unnngh_ ," Cas arched his hips, fucking nothing, his head thrown back at Dean's words and he was. So. Fucking. _Beautiful_. The line of his chest and ridge of his nipples, dusty on tan skin. His abdomen markless, blank from a month without Dean, and he needed to-mark him-he needed-

His mouth dropped to Cas stomach. His teeth nibbled bruises on flesh, licking, kissing, his demon tongue working just a little darkness into each nip and suck, just enough to make a mark that would last on a holy angel's regenerative body, enough that Castiel could see the stains of their unholy bond for _days_. Cas cried and whimpered as he did it-as he marked and marked and marked-head thrown side to side with the pain of it, but hands held down on Dean's head, urging him on, urging a claiming of his body. "Yours, Dean. _Mm_ , yours, always-forever- _Dean!_ " he babbled, muttering swears and promises and wordless cries until Dean couldn't take it anymore and he _needed_ Cas on his tongue.

He clawed at belt and zipper and ripped Cas' pants open. His fingers hooked in pants and boxers both, and he tugged and tugged down hard so they knocked Castiel's shoes to the floor and then fell in a puddle over them, leaving Cas naked except for the stupid honeybee socks Dean had gotten him that this Angel of the Lord always insisted on wearing. Yeah, _even_ during sex. Because he was a nerd, a stupid, sentimental, _perfect_ nerd. Dean kissed his knee before he focused again.

Castiel's cock waved in the air, and Dean turned his attention to it, licking his lips and watching it twitch and leak. He crawled up Cas' body and parted his mouth when Cas stopped him. "Wait. Dean, I-I need you too." Dean looked up at him and Cas wet his lips. "Together?" He wouldn't have said no before, but the soft, pleading question in cerulean eyes flooded Dean's mouth with saliva, and his eyes flicked briefly black.

"Yeah," he rumbled, his voice thick as he stripped off his pants and shoes and socks. He climbed on top of him, stopping to lick inside his mouth and cry with him at the throb of their dicks rubbing together. They writhed helplessly for a few desperate minutes, fucking each other with their dry dicks before Dean tore away from a pleading Cas and turned around so his cock could take the place his mouth previously was-hovering above Castiel's lips. He lined his own mouth up, but just as he was about to flick his tongue against the beading cum, burning slick dragged along the sensitive slit of his dick, and a shudder rippled from his hips. Cas wanted to tease, huh? Two could play that game. He licked his lips.

Usually, it was the other way around, him teasing the bejeezus out of Cas, and Cas just straight up going for it. Somehow, things were reversed tonight as Dean grabbed the base of Castiel's cock and sucked him to the back of his throat in one smooth move. Hips came off the mattress and fucked once, a hoarse cry of ache and pleasure spilling in the air, before that tongue returned to his shaft, still gentle, licking, sucking at his head, and then striping down the shaft. Dean groaned helplessly. He wasn't used to coy Cas. He wanted to fuck those lips of his until they were red. But the weight in his own mouth was so fucking fantastic after so long without, so he forgave Cas and started to bob. The taste of holy dick was somehow something he had grown a taste for unlike anything else. It hurt, yeah, like every single thing they did together, it burned his soft pallet and ravaged his throat, but he tasted so good, so-so _familiar_ -so Cas and _his_ alone, that Dean wanted it, wanted everything Cas would give him.

Finally, finally, after what seemed for fucking ever, Cas wrapped around him, and burning, suction heat sucked him down. Hands on his hips urging him til he was rocking into that mouth. He started bobbing faster as he started thrusting his hips and Cas groaned around him, and it felt _so good_.

It drove him crazy to do this, every time. And he could come like this, just like this, he could come so hard. Taking burning cock as he fucked Castiel's throat raw to the chorous of choking and swallowing and lapping and thunder outside. He knew his eyes were black, he felt them flick dark, but he couldn't help himself. He felt too fucking overwhelmed as his hips moved all on their own and Dean tried, tried to be gentle and _couldn't_ when he felt the aching wet burn of Castiel's mouth, tight around his shaft, wet musle working, laving whatever it could reach. Drool slipped from his own mouth and dribbled down the cock burning his lips, a quiet _hiss_ steaming from it as it dripped down and glistened on his balls. And wasn't that a lovely sight? He smiled around cock, took a breath and slid down all the way until Cas' cock filled his throat, just as his head hit the back of Cas' throat, and they both moaned.

Air was something Dean didn't really _need_ , per se, but he still choked, and his hips stuttered, pounding Cas' hot tongue. The whimper of raging arousal he tried to make turned out more of gurgle before he swallowed around his shaft, but Cas still made ten bruises on his hips and pushed him up and out of his mouth. "Dean- _Nnngh_ -Dean-stop."

Smirking as best he could, Dean tightened his lips and sucked until Cas made sounds of such pure eroctic content that his dick throbbed and his eyes rolled back in his head. "Dean-" Fingers dug harder. "Fuck me, please. Please-" the cry turned into a groan. "Make love to me," he whispered, hoarse and straining. Those words sent a warm flush to his cock, and he thrust his hips against Cas' lips, twitching at the accompanying burn, and pulled off of Cas dick, gasping for air on instinct.

"God, yes," he groaned and kissed the thighs below his face, making him twitch and leaving red marks behind, before grabbing the lube that had fallen from the bed to the floor. And ok, no, they didn't really _have_ to do this. Either of them could make Cas open and ready with a snap of their fingers, but Dean _wanted_ to. He wanted to feel that tight smooth channel gripping his fingers, sucking him in. He wanted to make Cas crazy, whining and begging-and, okay, there's the usual tease he was.

So he smiled at Cas as he slicked up his fingers. Cas smiled back, warm and flush with arousal, spreading his legs for him, ready, waiting, and somehow, in Dean's crazy heat-adled brain, something softened. God, he was perfect. Dropping the bottle, he climbed up Cas and pressed their lips together, shivering at the the electric shock that came with every kiss. Hands tangled in his hair and pulled him closer, and they kissed. They kissed and kissed as if they were human lovers, together, unafraid, unhurt by the other's touch.

"I love you," Cas said against his lips, and Dean smiled, feeling that soft thing inside of him soften more. He loved hearing that, the impossible, true. An angel of heaven in love with _him_. He stroked Cas' cheek and kissed him again, crying at the burn and nuzzling into his face for a moment with all the overwhelming affection he felt in return, ignoring the blood that welled to the edge of his thinning skin at the contact. Then he kissed down his chest and slid his lube-slick fingers up the crack of his ass, and Cas shivered, willingly spreading wider.

Dean circled his hole only once before pushing in, sooner and rougher than he would have if Castiel weren't an angel. But he was, and as much as Dean wanted to enjoy this, they needed this, needed each other, needed to be as close as possible while they could after so many days apart. And besides, Cas' hole might burn from his finger, but it sucked him in anyway. So perfect smooth and slick and _tight_ , pressing in on Dean while he held still, gritting his teeth as the sear wracked his skin. "Come-Come on-" Cas breathed, his eyes closed as he rocked on that finger. So Dean started moving, thrusting in and out and breathing heavy until he pushed in two, and Cas moaned. "I need you inside, Dean, please." But he couldn't-he _wouldn't_ -just yet.

"Not yet," he whispered, kissing Cas' stomach. He twisted his fingers and stretched, opening him quick and steady, thrusting every other twist to make Cas whimper and moan. He got it up to three lubed fingers thrusting hard and stretching wide before he started to lose his relative calm. His dick was throbbing and aching to come, and Cas was spread out before him, naked but for those stupid honeybee socks, his damp hair dripping on his face as he shifted between throwing his head back in pleasure or staring at Dean with dark eyes and _begging_. "Okay," Dean gasped, "Okay," and he pulled his fingers out. "Like this?" he asked, and Cas noddded, whined, squirmed on the brand new sheets.

"Fuck me."

 _God in heaven_. He didn't even care if Cas was the death of him. He'd take it, happily, to see him looking like this.

He slicked up his cock and lowered himself over Castiel, bracing himself on either side of his body. His cock brushed against Cas' ass, and they both gasped. "Look at me," he whispered, and Cas opened his eyes while Dean reached back and steadied himself, lined himself up. With their eyes locked together, he _pushed_. The glorious stretch worked for a second, Cas' eyes wide, before the head of his cock slid inside, and they both shuddered, spasming, holding their breath until they adjusted, pushed past the burn, Dean's eyes flicking from black to green again. And when Cas nodded, he slid in the rest of the way, bottoming out inside.

"You feel good," he growled, his eyes falling shut against his will.

"You burn," Cas whispered, and Dean's eyes popped back open. A different kind of pain sliced inside, and he lowered his forehead to Cas'.

"I know, I know, baby. I'm so sorry, _Nng_." It felt like his dick was wrapped in loving fire. Loving. But fire all the same. His demon blood trying to repel Castiel's angelic grace, and vice versa. It was impossible-or it should have been. Angels and demons didn't _do_ this. Fall in love. It was moronic. They could barely touch without crying at the hurt, and yet at the same time, they couldn't let go.

"It's ok," Cas said, hissed. "I know it's a part of being with you. I just-it hurts-and feels good. And hurts."

Dean understood completely. Better than anyone. In fact, he was pretty sure he was the only other being who could understand so well. It was agony, and pure, pure pleasure and need. They needed each other too much not to fight past the pain, but still, he would do just about anything to make it stop, stop hurting Cas.

He lowered his mouth and kissed him to distract him a bit, not that the burn would go down much while they were in contact, but it was the only thing he could do. And it seemed to help. Because Cas lifted his legs higher, wrapped them around Dean, and started pushing down on his cock.

 _Mmng_ , he didn't need to be told twice. He pulled back and started moving in Cas. A groan fell from his lips as the tight heat sucked him back in, just as it had done to his fingers. Despite the pain that was always there, it was so good with Cas. Whether or not he was doing the fucking-whether they were fucking at all-it was intense and all-encompassing and felt weirdly _good_. It shouldn't feel so good with who they were and what they were doing, but it did, somehow, it _ripped_ through his body in tumbling waves of pleasure. Nothing he had ever felt in his long life-and yeah, his life had been fucking long-was as good as this. Not even close.

" _God_ , Cas." He moved his lips down his neck and clamped down on Cas' shoulder, trying to keep his head, to keep him _grounded_ , to not _come_ within the first five minutes of fucking into him.

"Dean-it feels-so good!" Arms wrapped around him, clutching him close, as Dean fucked into him. Hips rose higher and knees slid up around Dean, ass raised up for the scorching pounding it was getting when-

" _AAahhhn_ , Dean! There-f-fuck-" His words cut off as he grit his teeth and keened when Dean hit that sweetspot again. And again. And again, again, again. And Cas' pleasure turned into a focus for Dean. He pounded that spot and lapped over the bite mark he made. He kissed and nibbled up Cas' neck, as his angel tilted his head back to give him more room to lick and suck and kiss.

"Cas, Cas, Cas," he murmured against his skin as he moved his lips up his jaw and his mouth found Cas'. He speared his tongue inside in a sloppy wet kiss, both of them rocking together, meeting each thrust, crying and clutching tighter.

"Close-" Cas gasped. "Close, Dean. Just need-" he moaned, and Dean slipped his hand down between their rolling bodies and gripped Cas' cock. Hissed at how fricken hot it was, and bit his own lip as he started stroking, fisting him in time with each thrust.

"'M close too, Cas," Dean gasped.

"So close, Dean-I-ah-" He gasped and closed his eyes. "K-Kiss me. Please. Kiss me." Cas pulled him down, and Dean crushed his mouth against chapped, slicked lips, groaning. Cas' tongue licked into his mouth, somehow in control when Dean was losing his mind. He licked inside, and Dean twisted his fist and fucked that spot, and Cas cried out, arching against him, skin and skin and skin, and white hot heat streaked along his abdomen. Cas cried and whimpered, and somehow didn't stop kissing him, and that was what threw Dean over the edge. His hips stuttered, and he peaked. Half groan, half wail worked up his throat as pleasure cascaded through his body. Come pulsed through his cock, and he came inside of Castiel.

* * *

They lay on their sides, facing one another, the tension gone from their muscles, but untired, ever, always untired. On the blue sheets their hands sit, a hairsbreadth apart, not touching, but close enough to feel the heat sparking in contrast. Close enough to singe, but neither willing to pull back.

This was common, after sex. They couldn't cuddle-well they _could_ , but after embraces of pain spiking through their skin and pleasure so intense the throb remained in their ever healing bodies for days, they needed space to breathe, to recover. But they could look. They could stare and study and search each other's eyes. And did, usually for hours or until one of them had to go.

Cas still wished he could curl his fingers with Dean's. Kiss each knuckle.

"What are you thinking?" he asked when Dean's eyes fell away.

His small smile was bitter as he fisted the sheet gently between them. "Usual angst, Angel. Hunting, angels, demons. This." His fingers flitted in the air to indicate the two of them. "You?"

"That I love you." He bumped their knuckles together, shivering at the cramp and wisp of burnt skin. Dean's eyes softened as he flexed his fingers, working the kink through.

"I know that. I don't fucking deserve it, but I know."

"I was also thinking... " Cas hesitated. It wasn't like this would be the first time they'd talked about it, but there was also a... "silent agreement" between them, as Dean said, that they wouldn't anymore. It was... "pointless," only caused sadness. But... Cas pursed his lips and looked away. "I wish I could touch you... without..."

"The pain." Dean's voice was sad, his eyes melancholy. "Me too, Angel."

"I know just wishing doesn't change anything, but..." Dean nodded and moved his hand just that much closer.

He didn't have to speak the words to say _I know. I understand_. And they didn't talk about it anymore. They lay together in reflective silence, not perfectly happy, but content enough to lose themselves in each other's eyes.

* * *

The storm was breaking when Castiel picked up on angel radio and would have to return to heaven. They were both melancholy as they stepped through the leaky shack towards the door. "I guess this is adios, huh?" A wave of regret made the words a little more bitter than Dean had intended them.

"For a little while, yes," Cas murmured, turning to face him.

"How longs a little while this time, Cas? A week? Another month?" The already slumped shoulders of Castiel's frame curled a little more. The ceruleans filled with such intense sadness Dean regretted his harsh tone instantly. _Stupid, stupid, stupid_. Cas didn't deserve that. They were both trying here, really fucking hard, in an already impossible situation. _You don't deserve him, jackass._ He swallowed past the lump in his throat and stared at Cas, willing his feelings to show. And something passed between them, some understanding, the longing so intense they always seemed to feel for one another, and they moved as one.

A flash of hands grabbing and arms twining, dragging them together until their lips met, hard, chapped and slightly bloody from the night before, burned from the hells fire of one and the holy fire of the other. Groans and whimpers leaked from their throats in the push, pull, shove, drag of their kiss. The pain pushing them apart, the want pulling them together.

Dean's back hit the door, somehow, he didn't know, because his nails were biting new moon scars in Cas' neck while his tongue twisted with Cas'. Salty sulfur and iron swished around his taste buds, some of it his, some of it Cas', all of burning on the way down, and Dean fisted Cas' hair and pulled him back, breaking away with, "Fucking hell!" in a groan of pain. Tears burned the edges of his vision, and he breathed through Cas-burned air, coughing. "Fuck, that bites," he hissed, when the throb had ebbed to a survivable medium.

He cracked his eyes open slowly, bearing the singe of his arm wrapped around his angel's neck and the palms pressed against his sides. Castiel's cheeks were flushed, his lips bloody and parted as he panted air, but his eyes-his eyes were bright and dark and longing.

"Dean. Will you be available tomorrow night?"

Dean smirked, ignoring the thrum of warm pleasure in his chest. "Why? Ya thirsty for more demon blood?"

"I'm thirsty and starving and desperate for you, Dean." He answered him without missing a beat, and the thrum turned into a symphony.

"Well, fuck." Dean eyed him warmly. Licked his lips and swallowed the blood. "How could I say no to that?"

Dean was graced with the holy grail-or in other words, the big, gummy rare!smile of Castiel. He nodded, and Dean let him through the door. His shadow wings spread wide around him, but Dean grabbed his hand before he could go, grimaced at the slight wince of pain, and Cas looked at him quizzically. Dean swallowed. "You know I'm in fucking love with you, right?"

His friggin smile got bigger. He pulled their twisted, cramping fingers together and kissed each of Dean's knuckles. "I know. I don't deserve it," he murmured, repeating Dean's words back to him, "but I know."

Dropping his hand, Cas turned and flew, disappearing into the ether in seconds. Still, for a long, long while, Dean stared after him.


End file.
